The catch with such schemes is that the initial positive effect may tend to diminish with time and if the"perceived" entitlement later fails to come to pass (targets missed etc) then a badly structured scheme can end up being worse than having no scheme, accordingly you are sensible to think it through very carefully in advance.

I was the beneficiary of such employer generosity in the 1990s that did not come to pass, a lot of promise and little delivery- as a result I left somewhat disillusioned.

I set up a scheme for one company I worked for in the early 1990s( retail clothing ) with mixed results, although measurement against targets sort of worked (Set monthly thresholds for each shop and staff shared 10% of sales revenues over targets in pre arranged ratios (Manager/assistant manager/ assistants)), such schemes will only be accepted by staff if target setting is deemed fair- the subjective part can be difficult.

The difficulty that an accounting practice has over say the sale of pullovers is the quality control of the service. In retail either number of units shifted or money received can be used as the performance measure, give or take increasing either tends not to impact the quality of the delivered product. But accounting services are different, if one motivates via time taken/fees earned then the "perceived" increase in productivity may run hand in hand with a diminished product quality ( Why check A,B, C and D if the time taken reduces my profit share?)

Also not sure that profit measurement is the way to go with all staff, for owner managed business entities choices made by the owner may have a significant impact on the operating profit, as these choices are outwith the control of the staff measuring by accounting profit may be grossly unfair. By fees issued is more within employee control but even here "serpents lurk", if one member of staff has a client portfolio of cleaner/easier clients, then his throughput may be much better than his harder working colleague who seems to have the client portfolio from hell- if perceived injustice re work allocation the scheme may also well falter.

I have no silver bullet but I do think the first thing is to fit the scheme to the working practices of your organisation, imho appending an alien scheme to your practice is the fastest way to disaster, so any scheme I believe has to be in sympathy with how things currently operate and needs to be fair and seen to be fair. Good luck.